[core] modify use of posix_spawnattr_setsigdefault

modify use of posix_spawnattr_setsigdefault() on __linux__

Subprocesses (CGI scripts and backends FastCGI, SCGI, proxy, etc)
which spawned their own children and accidentally relied on inheriting
SA_RESTART on SIGCHLD from lighttpd will now have to set that flag
themselves, if desired.

From a quick survey:
- bash sets SA_RESTART on SIGCHLD.
- Perl and Python unconditionally reset signals.
  (Other interpreters are expected to do so as well.)

1 files changed, 9 insertions, 0 deletions

diff --git a/src/fdevent.c b/src/fdevent.c
index f9de595e..85de850a 100644
--- a/src/fdevent.c
+++ b/src/fdevent.c
@@ -516,6 +516,14 @@ pid_t fdevent_fork_execve(const char *name, char *argv[], char *envp[], int fdin
        #endif
         && 0 == (rc = sigemptyset(&sigs))
         && 0 == (rc = posix_spawnattr_setsigmask(&attr, &sigs))
+      #ifdef __linux__
+        /* linux appears to walk all signals and to query and preserve some
+         * sigaction flags even if setting to SIG_DFL, though if specified
+         * in posix_spawnattr_setsigdefault(), resets to SIG_DFL without query.
+         * Therefore, resetting all signals results in about 1/2 the syscalls.
+         * (FreeBSD appears more efficient.  Unverified on other platforms.) */
+        && 0 == (rc = sigfillset(&sigs))
+      #else
         /*(force reset signals to SIG_DFL if server.c set to SIG_IGN)*/
        #ifdef SIGTTOU
         && 0 == (rc = sigaddset(&sigs, SIGTTOU))
@@ -528,6 +536,7 @@ pid_t fdevent_fork_execve(const char *name, char *argv[], char *envp[], int fdin
        #endif
         && 0 == (rc = sigaddset(&sigs, SIGPIPE))
         && 0 == (rc = sigaddset(&sigs, SIGUSR1))
+      #endif
         && 0 == (rc = posix_spawnattr_setsigdefault(&attr, &sigs))) {
 
           #if defined(HAVE_POSIX_SPAWN_FILE_ACTIONS_ADDCLOSEFROM_NP) \